NASA's space shuttle program was retired this past July after some three decades of spaceflight. The United States therefore remains dependent on Russia's Soyuz spacecraft to carry astronauts to and from the ISS - with Europe and Japan also providing unmanned cargo ships to haul supplies to orbiting station.

It should be noted that NASA has already clinched a deal with the privately owned Space X to fly 12 ISS delivery flights using its robotic Dragon space capsule and Falcon 9 rocket. The first flight is expected to launch by the end of 2011.

In addition, the space agency has also hired Orbital Sciences Corp. to fly 8 ISS cargo missions using its unmanned Cygnus spacecraft and Taurus 2 rockets. The first Cygnus mission to the space station could take places as early as February 2012.